High-field conduction and carrier traps in polyethylene copolymerized with various monomers

The electrical breakdown and electrical conduction of ethylene copolymers have been studied. The electric strength of ethylene copolymers containing an optimum content of halogen moieties such as bromophenyl and fluoroethylene groups was found to be higher than that of LDPE over the wide temperature range from ?196°C to 90°C. Also, conduction currents in the copolymers were suppressed at high electric fields. X-ray-induced thermally stimulated currents (TSC) revealed that halogen comonomers act as carrier traps with a depth of about 0.4 eV. Consequently, the introduction of comonomer-containing halogen groups into polyethylene suppresses electron acceleration as a result of an increase in trapping and scattering of conduction electrons. This leads to an increase in electric strength which is determined by the electron avalanche breakdown.     

SIMULTANEOUS HEAT AND MASS TRANSFER IN LAMINAR GAS STREAMS IN WETTED-WALL COLUMNS

In the previous papers (Hikita and Ishimi,1976b; 1978, Hikita et al., 1979), the results of theoretical analysis of the mass transfer rate in laminar gas streams in wetted-wall columns have been reported. The similarity of the forms of the basic differential equations for mass and heat transfer makes it possible to apply the results of the mass transfer analysis to the heat transfer analysis. The present study was undertaken to confirm the above analogy between mass and heat transfer experimentally, and to investigate the effect of the gas and liquid flow rates on the heat transfer rate in laminar gas streams in wetted-wall columns.     

Phase transfer agents. II. Stereospecific hydroxylation of oleyl and elaidyl alcohol and periodic acid cleavage of epoxides

Oleyl and elaidyl alcohol have been stereospecifically hydroxylated by cold, dilute alkaline potassium permanganate toerythro- andthreo-9,10-dihydroxyoctadecanol, respectively, in 40–80% yields in a water-methylene chloride heterogeneous system. Phase transfer agents (PTA) were used to transport permanganate ion from the aqueous to the organic phase. In the absence of PTA, hydroxylation did not take place. Periodic acid cleavage of epoxides in a water-methylene chloride system was studied in the absence and presence of PTA. At slow stirring rates PTA exert a rate accelerating effect in cleaving certain epoxides to aldehydes but with vigorous stirring use of PTA has only a marginal advantage.     

Phase transfer agents. I. Transfer of permanganate,periodate, and cyanate ions from aqueous to organic phases. Preparation of quaternary onium periodates

Several quaternary ammonium and phosphonium halides have been shown to be useful phase transfer agents (PTA) for the efficient transport of permanganate, periodate, and cyanate ions from aqueous to organic phases (benzene and/or methylene chloride). Chemical and spectral methods of analysis were used to measure ion transfer quantitatively and to assess the relative efficiency of PTA.     

Mechanochemical block copolymerization in heterogeneous systems of the solid poly(vinyl chloride) with styrene by ultrasonic irradiation

Summary Mechanochemical block copolymerization in heterogeneous systems of the solid poly(vinyl chloride)-styrene-sodium dodecyl sulfate aqueous solutions has been studied by ultrasonic irradiation at 65 °C. The block copolymerization of styrene was initiated by free radicals produced from the poly(vinyl chloride) particles by ultrasonic waves. The initial rate of the block copolymerization Rp was given by Rp α [Styrene] [Sodium dodecyl sulfate]^1/2. Both copolymer and homopolymer were obtained. For example, when 2.506 g of the poly(vinyl chloride) particles, 24.23 g of styrene, and 54.00 g of sodium dodecyl sulfate aqueous solution (0.500 wt%) were added in the reaction system, the weight proportions of the block copolymer and polystyrene after 60 min were approximately 50 and 20%.     

A simple method for minimizing non-linear image contrast in spherical aberration-corrected HRTEM

A simple and practical method for minimizing non-linear image contrast in spherical aberration-corrected (C(S)-corrected) high-resolution transmission electron microscopy is presented. The effectiveness of the method is considered from the viewpoints of theoretical formulations and image simulations including second-order imaging effects. The method is one of the advantages of C(S)-correction and applied to high-resolution images down to 0.1 nm. The dynamical diffraction effect is carefully evaluated, which shows that the phase deviation of diffracted waves from pi/2 violates the present method in thicker crystals over approximately 10 nm.     

Resonant s.a.w. filter using surface shear wave mode on LiTaO3 substrate

A low-loss narrow band (below 3%) resonant filter has been achieved using twin-turn reflectors and a surface shear wave mode on 36° YX LiTaO3 substrate.     

Spray Pyrolysis of Fe3O4–BaTiO3 Composite Particles

Fe₃O₄–BaTiO₃ composite particles were successfully prepared by ultrasonic spray pyrolysis. A mixture of iron(III) nitrate, barium acetate and titanium tetrachloride aqueous solution were atomized into the mist, and the mist was dried and pyrolyzed in N₂ (90%) and H₂ (10%) atmosphere. Fe₃O₄–BaTiO₃ composite particle was obtained between 900° and 950°C while the coexistence of FeO was detected at 1000°C. Transmission electron microscope observation revealed that the composite particle is consisted of nanocrystalline having primary particle size of 35 nm. Lattice parameter of the Fe₃O₄–BaTiO₃ nanocomposite particle was 0.8404 nm that is larger than that of pure Fe₃O₄. Coercivity of the nanocomposite particle (390 Oe) was much larger than that of pure Fe₃O₄ (140 Oe). These results suggest that slight diffusion of Ba into Fe₃O₄ occurred.     

Fabrication of electrochemically stable fluorinated nano-carbon film compared with other fluorinated carbon materials

We fabricated electrochemically stable fluorinated nano-carbon film that had an sp² and sp³ hybrid nanocrystalline structure formed using the electron cyclotron resonance (ECR) sputtering method. This fluorinated ECR (F-ECR) nano-carbon film prepared with a short CF₄ plasma treatment has a high fluorine content (F/C:0.20) and a low oxygen content (O/C:0.02) on its surface and retains its original morphology. This F-ECR nano-carbon is capable of a lower capacitance current, and a wider potential window than untreated ECR nano-carbon. The electron transfer rates at an F-ECR electrode are as high as those of untreated carbons for , whereas they are much slower than those of untreated ECR nano-carbon for Fe^2+/3+ and owing to its selective sp² fluorination. These slow electron transfer rates for Fe^2+/3+ and are maintained during potential cycles due to its robust nanocrystalline structure. In contrast, these slow electron transfer rates were easily recovered for fluorinated glassy carbon under same condition. Furthermore, a smaller fluorination effect was observed for polycrystalline boron-doped diamond owing to the low reactivity of its sp³ bonds. Our ECR nano-carbon film is suitable for the effective fabrication of a fluorinated surface while maintaining a relatively active electrochemical interface and excellent stability.     

Cathodic performance of LiMn1−xMxPO4 (M = Ti, Mg and Zr) annealed in an inert atmosphere

To improve the cathodic performance of olivine-type LiMnPO₄, we investigated the optimal annealing conditions for a composite of carbon with cation doping. Nanocrystalline and the cation-doped LiMn_1−xM_xPO₄ (M = Ti, Mg, Zr and x = 0, 0.01, 0.05 and 0.10) was synthesized in aqueous solution using a planetary ball mill. The synthesis was performed at the fairly low temperature of 350 °C to limit particle size. The obtained samples except for the Zr doped one consisted of uniform and nano-sized particles. The performance of LiMnPO₄ was much improved by an annealing treatment between 500 and 550 °C with carbon in an inert atmosphere. A small amount of metal-rich phosphide (Mn₂P) was detected in the sample annealed at 900 °C. In addition, 1 at.% Mg doping for Fe enhanced the rate capability in our doped samples. The discharge capacity of LiMn_0.99Mg_0.01PO₄/C was 146 mAh/g at 0.1 mA/cm² and 125 mAh/g even at 2.0 mA/cm².